Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$156.48	10.301%	$172.599	$172.60	$172.60	$172.60
Purchase #2	$110.45	11.868%	$123.5582	$123.56	$123.55	$123.60
Purchase #3	$216.55	6.874%	$231.4356	$231.44	$231.45	$231.40
Purchase #4	$67.79	11.306%	$75.4543	$75.45	$75.45	$75.50
Purchase #5	$134.59	5.729%	$142.3007	$142.30	$142.30	$142.30
Purchase #6	$215.56	6.163%	$228.845	$228.85	$228.85	$228.80
Purchase #7	$148.83	10.493%	$164.4467	$164.45	$164.45	$164.40
7 purchase totals =	$1,050.25		$1,138.6395	$1,138.65	$1,138.65	$1,138.60